1. Field of the Invention
The present invention relates to a light-source device for illuminating a light valve means, such as DMD, used in a projection type display device.
2. Description of the Related Art
A Digital Micromirror Device, known as DMD (a trademark of Texas Instruments Incorporated), is widely used in the projection type display device. DMD has an array of micron square movable micromirrors of 16 xcexcmxc3x9716 xcexcm fabricated on a silicon substrate. Each micromirror is stable in one of two positions, wherein a source light directed upon the mirror array will be reflected in one of two directions. In one stable xe2x80x9conxe2x80x9d mirror position, light will be reflected to a projection lens and focused on the screen. In the other xe2x80x9coffxe2x80x9d mirror position, light directed on the mirror will be deflected to a light absorber. Each individual micromirror corresponds to one pixel and collectively forms an image by reflecting the light in two directions.
A light-source device for illuminating the light valve as DMD uses a rod integrator to improves the uniformity of the source light (refer to U.S. Pat. No. 5,634,704 for details).
Each micromirror forms xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d mirror position by tilting at the angles as small as +10xc2x0 and xe2x88x9210xc2x0. Therefor, if the incident light on the DMD has wide angular distribution, each micromirror can not reflect the light in the accurate direction. As a result, the contrast of the projected image decreases.
It is therefor, a primary object of the invention to provide a light-source device, which is capable of providing a source light having uniform brightness of which incident angle has narrow distribution.
This object is achieved in accordance with one aspect of the present invention which is a light-source device comprising: a rod integrator having an injection end and an emitting end; a lens unit for collecting a luminous flux emitted from the emitting end; and, a diaphragm. The rod integrator forms a plurality of imaginary light-source points, each of which virtually emits the luminous flux toward the emitting end. The diaphragm is disposed in the vicinity of a plane on which the lens unit forms the images of the imaginary light-source points, and selectively blocks luminous flux emitted from each of the images of the imaginary light-source points.
In another aspect of the present invention is A projection type display device comprising: a rod integrator having an injection end and an emitting end; a lens unit for collecting a luminous flux emitted from the emitting end; a diaphragm; a light valve means disposed in the vicinity of the plane on which the lens unit forms an image of the emitting end; and, a projection means. The rod integrator forms a plurality of imaginary light-source points, each of which virtually emits the luminous flux toward the emitting end. The diaphragm is disposed in the vicinity of a plane on which the images of the imaginary light-source points are formed, and selectively blocks luminous flux emitted from each of the images of the imaginary light-source points.